Compound Interest Calculator
Project future value and interest earned with annual, monthly, or daily compounding. No contributions or fees. Results stay in your browser.
1. Enter values
%
2. Result
Future value
16,470.09
6,470.09
10,000
12
3. Summary
How is it calculated?
Future value uses A = P (1 + r/n)^(n t). Interest earned is A minus P. This ignores contributions, fees, and taxes, and it is not a bank APY quote.
Common use cases
Savings growth
See what a deposit becomes if you leave it untouched.
Exam problems
Annual compounding matches typical textbook setups.
Compounding frequency
Monthly versus annual n changes the future value slightly.
Goal setting
Work backward from a target by trying different years.
Cash products
Daily n approximates some savings-account conventions.
Planning only
This is a projection in the tab, not investment advice.
Your data stays private
Principal and rates are projected locally in your browser. Nothing is uploaded or stored on a server.
About compound interest
Compound interest pays interest on interest. The textbook formula is A = P (1 + r/n)^(n t), where r is the nominal annual rate as a decimal, n is compounding periods per year, and t is years. Monthly compounding (n = 12) is common for savings accounts; daily (n = 365) appears in some cash products; annual is typical in exam problems. Interest earned is A − P.
This model ignores contributions, withdrawals, fees, and taxes. It is not APY advertised by a bank (APY already folds compounding into one yearly percent). It is also not a loan amortization: borrowing uses the payment formula on Loan Calculator. Very high n with long t can overflow ordinary floating point — keep inputs realistic.
Use it to compare “what if I leave this deposit for ten years?” scenarios. Results stay in the browser. We do not connect to market data.
How to project compound interest
Enter principal, rate, and years
Rate is a nominal annual percent. Years can be a fraction.
Choose compounding
Annual, semiannual, quarterly, monthly, or daily. More frequent compounding grows slightly faster.
Read future value and interest
Copy the future value. Examples include monthly vs annual. Calculate jumps to the result.
Projections stay here
No account data is uploaded. This is not investment advice.
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Compound Interest Calculator FAQ
Annual (n=1), semiannual (2), quarterly (4), monthly (12), and daily (365). The formula is A = P (1 + r/n)^(n t) with r as a decimal annual rate and t in years. Interest earned is A − P. Monthly compounding is common for savings; more frequent n grows slightly faster at the same nominal rate.
No. There are no recurring contributions, withdrawals, taxes, or advertised APY (APY already folds compounding into one yearly percent). This is also not a loan payment — use Loan Calculator to amortize debt. Keep inputs realistic; extreme n and t can overflow ordinary floating point.
No. Projections run locally in your browser. Nothing is uploaded or stored on a server. This is not investment advice.